In order to guarantee that an evolved mobile communication system may satisfy the continuously increasing requirements of users in a long term of future, the ability of possessing rapid increasing IP data service by the evolved mobile communication system should be enhanced, and the employment of packet technology in the mobile communication system should be further improved. The most important parts in this kind of technology evolution include: reducing time-delay and latency time, increasing user data rate, increasing system capacity, enlarging coverage area, and decreasing overall cost of the operator. Besides, the backward compatibility of the evolved network architecture to the existing network is also an important consideration.
In a 3GPP system prior to the evolved network, an attaching process and a Packet Data Protocol (PDP) context activating process are two separated processes. Once powered on, a terminal firstly performs a General Packet Radio Service (GPRS) attaching process, which mainly includes a security process and a location updating process. When the attaching process is completed, the terminal does not simultaneously acquire an IP bearer. Only when the terminal further initiates the PDP context activating process, the terminal may be provided with an IP address and corresponding configuration parameters. This is to say, it is necessary for a user to perform the PDP context activating process before service communication, resulting in a relatively long time-delay for the user to turn from an idle state to a data communication state, this definitely does not meet the requirements of the evolved network.
In order to reduce the latency time for a mobile terminal to turn from the idle state into the data communication state, a network registration and a default IP bearer establishment are performed together in a System Architecture Evolution (SAE)/long-term evolution (LTE) system proposed in a Specification, i.e., during the mobile terminal attaches to the network for the first time, the network allocates an IP address and some corresponding bearer resources to the mobile terminal. In this case, it is not specified whether or not the air-interface resource should be allocated. Thus, it is realized that the mobile terminal is always online, so as to provide service more quickly and rapidly by the network when the mobile terminal needs to perform data service. In short, it is at the time a user in the evolved network performs a network attaching process that a default IP bearer should be established. As illustrated in FIG. 1, the 3GPP Technology Report (TR) 23.882 made by 3GPP SA2 group provides a possible process of network attaching suggested by the current 3GPP TR (23.882) as follows:
(1) Network Discovery and Access System Selection: a terminal of a mobile user discovers SAE/LTE access systems and then performs access system and network selection.
(2) Attaching Request: the terminal initiates an Attaching Request, which includes old registration information of the user (for example, temporary ID), to a Mobility Management Entity/User Plane Entity (MME/UPE). The Attaching Request includes a permanent ID of the user if the terminal does not report the old registration information of the user. The Attaching Request may include information for default IP bearer (for example, IP address or APN selected by the user).
(3) a. Sending old registration information: if the old registration information of the user is reported by the terminal, the MME/UPE derives the address of an old MME/UPE registered last time from the old registration information of the user, and sends the registration information of the user to the old MME/UPE so as to ask for the information of the user.
b. Sending user context information: the old MME/UPE sends the context information of the user to the new MME/UPE, and the context information includes the permanent ID of the user, security context parameters, and so on.
(4) Security Functions (this step is optional): the new MME/UPE performs security authentication on the mobile user and equipment according to system configuration.
(5) MME Registration Updating: the new MME/UPE initiates a registration updating request toward a Home Subscriber Server (HSS), and registers as the MME/UPE currently serving the mobile user.
(6) Deleting user registration information: the HSS instructs the old MME/UPE to delete the context information of mobile user.
(7) Registration Confirmation: the HSS confirms the registration of the new MME/UPE. The subscription information for the default IP bearer, the relevant Quality of Service (QoS) strategy and the charging control information are also sent to the MME/UPE.
(8) Selection of Intersystem Mobility Anchor: An Inter AS Anchor is selected, and the selection mechanism is not specified. The IP address configuration is determined based on user's preference or subscribed data, or based on the strategy of Public Land Mobile Network (PLMN) or VPLMN.
(9) User Plane Routing Configuration: the Inter AS Anchor performs the IP layer configuration according to the determined IP address of the user. The User Plane is established and the basic strategies and charging rules are applied. It is not specified whether the establishment of the User Plane is initiated by the terminal or by the MME/UPE.
(10) IP Bearer QoS Configuration: the MME/UPE provides QoS Configuration of a default IP bearer (for example, the upper limit of data rate) to an evolved RAN. It is not specified whether a trigger mechanism is needed for this QoS Configuration (for example, it is needed when sending uplink or downlink data).
(11) Attachment Accept: the MME/UPE sends an attachment accept message indicating the acceptance of the terminal, and allocates a temporary ID for the terminal, the user's IP address is also sent to the terminal. In a roaming scene, roaming restrictions are checked, and the attachment is denied if the restrictions are violated.
(12) Attachment Confirmation: the terminal confirms the success of the attachment.
In the evolved network, the default IP bearer established during the user attaching process may bear IP-based protocol signaling, such as SIP protocol used by IP Multimedia Subsystem (IMS), as well as other potential services which may adopt default QoS controlling strategy and charging strategy. The QoSs required by upper layer application services are different largely from each other, and usually cannot be satisfied by the QoS provided by the default IP bearer. But the mobile user may continuously adopt the secondary PDP activating process which is similar to the existing process, based on the default IP bearer which has already been established, to accelerate the subsequent establishment processes for other service bearers and enhance the reaction speed of the system. Since the services established by the secondary activating process needs to share the IP address used by the first activating process, the IP address allocation strategy for the default IP bearer acquired in the registering process of the mobile user is very important, in that the strategy directly decides the data plane routing of the services of default IP address.
In order to improve the service quality for a roaming user, the evolved network requires the ability for optimizing the user plane routing of the roaming user. For example, the data of the roaming user are transmitted to the destination directly through the roaming network, rather than being routed back to the home network. Practically, the optimization of the user plane routing need be controllable for the home network of the user, so as to guarantee the benefits of the home network operator. However, there are no definite strategy and method to realize this optimization at present.